Fault Protection of Monolithic Audio Power Amplifiers in Severe Environments

Monolithic power operational amplifiers used in automotive AM-FM stereo receivers require protective mechanisms to assure performance in severe environments. Such protective mechanisms were developed and incorporated in an audio module after the identification of five major fault categories. The module, containing two operational amplifiers to meet radio power requirements, has seven reference comparators along with the necessary output control circuitry on a single silicon die. The comparators not only sense excess voltage on the power source, current, and temperature extremes but output load faults as well. A discussion of the environment, fault categories, control requirements, and fault detection means used to obtain the objectives follows.